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- Adamovic, Tatjana, 1974, et al.
(författare)
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Nonrandom pattern of chromosome aberrations in 17beta-estradiol-induced rat mammary tumors: indications of distinct pathways for tumor development.
- 2007
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Ingår i: Genes, chromosomes & cancer. - : Wiley. - 1045-2257 .- 1098-2264. ; 46:5, s. 459-69
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Tidskriftsartikel (refereegranskat)abstract
- Estrogens play an important role in breast cancer etiology and the ACI rat provides a novel animal model for defining the mechanisms through which estrogens contribute to mammary cancer development. In crossing experiments between the susceptible ACI strain and two resistant strains, COP (Copenhagen) and BN (Brown Norway), several quantitative trait loci (QTL) that affect development of 17beta-estradiol (E2)-induced mammary tumors have been defined. Using comparative genomic hybridization (CGH), we have analyzed cytogenetic aberrations in E2-induced mammary cancers and have found clear patterns of nonrandom chromosomal involvement. Approximately two thirds of the tumors exhibited copy number changes. Losses of rat chromosome 5 (RNO5) and RNO20 were particularly common, and it was found that these two aberrations often occurred together. A third recurrent aberration involving proximal gain and distal loss in RNO6 probably defined a distinct subgroup of tumors, since it never occurred in combination with RNO5 loss. Interestingly, QTL with powerful effects on mammary cancer development have been mapped to RNO5 and RNO6. These findings suggest that there were at least two genetic pathways to tumor formation in this rat model of E2-induced mammary cancer. By performing CGH on mammary tumors from ACI rats, F1 rats from crosses between the ACI and COP or BN strains and ACI.BN-Emca8 congenic rats, which carry the BN allele of the Emca8 QTL on RNO5 on the ACI genetic background, we were able to determine that the constitution of the germ line influences the pattern of chromosomal aberrations.
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| 2. |
- Adamovic, Tatjana, 1974, et al.
(författare)
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Oncogene amplification in the proximal part of chromosome 6 in rat endometrial adenocarcinoma as revealed by combined BAC/PAC FISH, chromosome painting, zoo-FISH, and allelotyping.
- 2005
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Ingår i: Genes, chromosomes & cancer. - : Wiley. - 1045-2257 .- 1098-2264. ; 44:2, s. 139-53
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Tidskriftsartikel (refereegranskat)abstract
- The inbred BDII rat is a valuable experimental model for the genetic analysis of endometrial adenocarcinoma (EAC). One common aberration detected by comparative genomic hybridization in rat EAC was gain/amplification affecting the proximal part of rat chromosome 6 (RNO6). We applied rat and mouse chromosome painting probes onto tumor cell metaphase preparations in order to detect and characterize gross RNO6 aberrations. In addition, the RNO6q11-q16 segment was analyzed by fluorescence in situ hybridization with probes representing 12 cancer-related genes in the region. The analysis revealed that seven tumors contained large RNO6-derived homogeneously staining regions (HSRs) in addition to several normal or near-normal RNO6 chromosomes. Five tumors (two of which also had HSRs) exhibited a selective increase of the RNO6q11-q16 segment, sometimes in conjunction with moderate amplification of one or a few genes. Most commonly, the amplification affected the region centered around band 6q16 and included the Mycn, Ddx1, and Rrm2 genes. A second region, centering around Slc8a1 and Xdh, also was affected by gene amplification but to a lesser extent. The aberrations in the proximal part of RNO6 were further analyzed using allelotyping of microsatellite markers in all tumors from animals that were heterozygous in the proximal RNO6 region. We could detect allelic imbalance (AI) in 12 of 20 informative tumors, 6 of which were in addition to those already analyzed by molecular cytogenetic methods as described. Our findings suggest that increase/amplification of genes in this chromosome region contribute to the development of this hormone-dependent tumor.
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| 3. |
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| 4. |
- Andreassen, A., et al.
(författare)
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2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) induces genetic changes in murine intestinal tumours and cells with ApcMin mutation
- 2006
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Ingår i: Mutat Res. ; 604:1-2, s. 60-70
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Tidskriftsartikel (refereegranskat)abstract
- 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is one of the mutagenic heterocyclic amines derived from cooked meat. In previous animal studies, spontaneous tumour formation in B6(Min/+) mice was associated with somatic loss of the wild-type Apc+ allele by loss of the entire chromosome 18 or by recombination. The objective of this study was to examine genetic changes caused by PhIP-exposure in a mouse intestinal cell line and in tumours from hybrid mice by keeping track of the chromosomes carrying the two Apc alleles. We transformed the SV40 T-immortalised intestinal epithelial cell line IMCE, derived from the B6(Min/+) mice by exposure to N-OH-PhIP, and studied the effect on Apc status and chromosome 18. Eighteen transformed cultures were obtained and all of them had retained the Apc+ allele. Five of seven transformed cultures were tumorigenic after implantation in nude mice. Chromosomal analysis of these five cultures and the parent IMCE cell line showed that the IMCE cells were near-tetraploid with an average of 77 chromosomes/cell, while the tumorigenic cell cultures were all triploid to hyper-triploid with a range of 61-69 chromosomes/cell. The number of copies of chromosome 18 was about four in the IMCE line and this copy number was retained in the transformed lines derived from IMCE. Changes in chromosome 18 and Apc during tumour development in vivo were examined in spontaneously formed and PhIP-induced intestinal tumours from two hybrid mice strains, i.e. B6(Min/+) - a murine FAP model - crossed with either AKR/J or A/J. We evaluated the allelic status of Apc, and the heterogenic microsatellite markers D18Mit19 and D18Mit4, located at the upper and lower ends of chromosome 18, respectively. In tumours from untreated animals, instability in the D18Mit19 and Apc was observed. Upon PhIP exposure, the B6(Min/A+) hybrid mouse tumours differed distinctly in genetic profile from those obtained from untreated animals and we detected three genetically different tumour groups, all of which had apparently retained Apc+. One group had allelic balance between the Apc(Min) and Apc+, the second had allelic imbalance between the Apc and D18Mit4 alleles, indicative of chromosomal stability in the first group and instability in the lower end of chromosome 18 in the second group, respectively. The third group showed variable allelic status of the three markers. A similar change in genetic profile was also seen in intestinal tumours of PhIP-exposed B6(Min/AKR+) hybrid mice, but it was less pronounced. Chromosomal breaks and/or recombinational events could be alternative explanations for the observed allelic imbalances in chromosome 18 markers in intestinal tumours from PhIP-exposed mice.
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| 5. |
- Hamta, Ahmad, 1961, et al.
(författare)
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Chromosome ideograms of the laboratory rat (Rattus norvegicus) based on high-resolution banding, and anchoring of the cytogenetic map to the DNA sequence by FISH in sample chromosomes.
- 2006
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Ingår i: Cytogenetic and genome research. - : S. Karger AG. - 1424-859X .- 1424-8581. ; 115:2, s. 158-68
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Tidskriftsartikel (refereegranskat)abstract
- A detailed banded ideogram representation of the rat chromosomes was constructed based on actual G-banded prometaphase chromosomes. The approach yielded 535 individual bands, a significant increase compared to previously presented ideograms. The new ideogram was adapted to the existing band nomenclature. The gene locus positions in the rat draft DNA sequence were compared to the chromosomal positions as determined by dual-color FISH, using rat (RNO) chromosomes 6 and 15 and a segment of RNO4 as sample regions. It was found that there was generally an excellent correlation in the chromosome regions tested between the relative gene position in the DNA molecules and the sub-chromosomal localization by FISH and subsequent information transfer on ideograms from measurements of chromosomal images. However, in the metacentric chromosome (RNO15), the correlation was much better in the short arm than in the long arm, suggesting that the centromeric region may distort the linear relationship between the chromosomal image and the corresponding DNA molecule.
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| 6. |
- Hamta, Ahmad, 1961, et al.
(författare)
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Cytogenetic aberrations in spontaneous endometrial adenocarcinomas in the BDII rat model as revealed by chromosome banding and comparative genome hybridization
- 2005
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Ingår i: Cancer Genet Cytogenet. ; 159:2, s. 123-8
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Tidskriftsartikel (refereegranskat)abstract
- Female rats of the inbred strain BDII are genetically predisposed to endometrial estrogen-dependent adenocarcinomas (EAC). More than 90% of them spontaneously develop this tumor type before the age of 24 months. In order to dissect out the genetic components behind these tumors we have made crosses between BDII females and rats from 2 other strains that are nonsusceptible to EAC. It was found that EAC tumors developed in a subset of intercross and backcross animals from both interstrain crosses. The chromosomal changes in the developing tumors were studied using cytogenetic and molecular cytogenetic methods. From these studies, we conclude that certain chromosome regions were recurrently engaged in chromosomal changes such as increases in copy number (e.g., trisomy, amplification) or decreases (e.g., deletion). Based on the analysis of 56 tumors, 8 regions were found to be particularly often involved: RNO4prx, gain=34 (61%) (amplification 12 cases); RNO5mid, loss=15 (27%); RNO6prx, gain=25 (45%) (amplification 8 cases); RNO10 loss, prx-mid/gain dst=25 (45%) (amplification 1 case); RNO12q, gain=23 (41%); RNO15p loss/RNO15q gain=29 (52%) (amplification 1 case) [RNO, rat chromosome; prx, proximal; mid, middle; dst, distal; p, short arm; q, long arm]. We begun to analyze these regions in detail using various molecular methods and within them there are certain possible target genes, such as MET (RNO4q21), CDKN2A/2B (RNO5q32), MYCN (RNO6q15 approximately q16), and TP53 (RNO10q24 approximately q25), but it is clear that several other genes, still unidentified, must also be involved.
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